With the ubiquity of the Internet and computer networks, electronic mail (email) is rapidly becoming the preferred method of communicating textual, graphical and other digital information. Unlike conventional postal mail, email may arrive at its destination within seconds or minutes of its sending, even where the recipient is across the globe. Moreover, an email may be easily sent to multiple recipients. Most enterprise service providers now support an email application program providing email accounts for its subscribers.
A conventional email system operates using a mail user agent, or MUA, which is a software application program used to send and receive emails. Examples include Outlook® messaging and collaboration client and Hotmail® web-based e-mail service by Microsoft Corporation, Redmond, Wash. An email includes a body with the email message, and a header having information such as “From” followed by a sender name, “To” followed by a recipient name, the message subject and a date stamp. The header may also include a sender email address and a recipient email address. An email address consists of a username followed by the “@” sign, followed by a domain name. The “To” and “From” names may or may not be the same as the sender email address and recipient email address. The email addresses are used for delivery of an email to its intended recipient(s).
Referring to FIG. 1, once an email sender creates an email using an MUA 20 listing one or more recipients, the MUA formats the message, including sender and recipient information, using the Simple Mail Transfer Protocol (SMTP) and sends the message to a local mail transfer agent (MTA) 22. The MTA 22 is a software agent, running on a mail exchange server of the sender's ISP, used to transfer email from the sender's MUA 20 to one or more recipients using the email address in the header. The MTA 22 contacts a domain name server (DNS) 24 for the domain listed in a recipient email address to find the mail exchange server(s) accepting messages for the domain specified in the email address.
The DNS 24 responds with a mail exchanger record (MX) listing the mail exchange server 26 for that domain. The MTA 22 may then send the message using SMTP to MTA 28 running on a mail exchange server of the recipient's ISP. The MTA 28 may then deliver the message to the recipient's mailbox on recipient's MUA 30 using for example the Post Office Protocol (POP3). Instead of traveling directly from the sender's mail server to the recipient's mail server, the message may travel through a number of intermediate mail servers. In addition to the sending and receiving IP addresses, the IP address of any mail server through which the message passes is also embedded in the header.
When sending or exchanging emails, there are instances where two or more parties may wish to communicate anonymously. Such instances may include business transactions or social exchanges where the parties may or may not know each other, but both parties wish to keep their real email address anonymous during the sending and/or exchange of messages. Moreover, one or more of the email participants may wish to place restrictions on the exchange, such as for example blocking emails from certain participants and limiting the number of emails which may be received from one or more participants.